Microelectronic integrated circuits may be subdivided into macro-blocks and individual cells. Macro-blocks are modules to be used in circuit designs which are standardized and therefore readily available. Macro-blocks are functional circuit blocks such as a central processing unit (CPU), random access memory (RAM), read only memory (ROM), or non-volatile memory (NVM). A cell may be a single circuit element or a group of one or more circuit elements such as transistors, capacitors, and other basic circuit elements grouped to perform a function. A cell may represent a single logical element such as a gate, inverter, or static random access memory (SRAM).
Microelectronic integrated circuits consist of a large number of electronic components that are fabricated by layering several different materials on a silicon substrate. Part of the design of an integrated circuit transforms a circuit description into a geometric description which is known as a layout. A layout comprises a set of planar geometric shapes in several layers.
The cells and other elements of a circuit are interconnected or routed in accordance with the logical design of the circuit to provide the desired functionality. The various elements of the circuit are interconnected by electrically conductive lines that are routed through vertical channels and horizontal channels that run between the elements.
Cells can be arranged in an individual manner or in a homogeneous manner. Cells arranged in a homogenous manner may be a cell array and more specifically a dynamic random access memory (DRAM) or SRAM array, for example. The underlying design principles for organization and arrangement of a homogenous cell array may be different than those of an individually designed logic array.